Heat sink and electronic device with heat sink

ABSTRACT

A heat sink includes a heat receiving part for receiving heat from the outside, a first radiating part, connected to said heat receiving part, which forms a first air channel, and radiates the heat from said heat receiving part using air that passes through the first air channel, and a second radiating part, located apart from said heat receiving part and connected to said first radiating part, said second radiating part forming a second air channel which the air that has passed the first air channel enters, the second air channel being narrower than the first air channel, said second radiating part radiating the heat from said first radiating part.

[0001] This application is a continuation based on PCT InternationalApplication No. PCT/JP00/09374, filed on Dec. 27, 2000, which is herebyincorporated by reference herein in its entirety as if fully set forthherein.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to heat radiatormechanisms, and more particularly to a heat radiator mechanism forradiating the heat from an exoergic circuit element or exoergiccomponent mounted in an electronic apparatus. The present invention issuitable, for example, for a heat sink that radiates the heat fromvarious exoergic circuit elements on a printed board in a personalcomputer (“PC”).

[0003] PCs are broadly available in the market as a typical informationprocessor. A motherboard or main board in the PC is mounted with variouscircuit components such as a CPU socket, a variety of memory (sockets),a chipset, an expansion slot, and a BIOS ROM, and directly affectsperformance and functions of the PC.

[0004] Recent PCs tend to include an increased number of exoergiccomponents and to generate more calorific values from them as variouscircuit components mounted on the motherboard provide higher speed andperformance. The heat destabilizes operations of circuit components, andfinally lowers the operational performance of a PC. Therefore, the PCprovides the motherboard with a heat radiator mechanism called a heatsink in order to thermally protect the exoergic components and othercircuit components mounted directly or via a socket or the like on themotherboard.

[0005] A description will be given of a conventional typical heat sink500 with reference to FIGS. 18 and 19, and another conventional heatsink 600 with reference to FIGS. 20 and 21. Here, FIGS. 18 and 19 areschematic side and plane views of the heat sink 500. FIGS. 20 and 21 areschematic side and plane views of the heat sink 600. The heat sinktypically includes plural cooling or radiating fins (or sometimes called“fin assembly”) made of a material having high heat conductivity, andcools exoergic components by forced or spontaneous air cooling. The heatsink 500 includes a base 510 placed on an exoergic component (not shown)mounted on a motherboard (not shown), and a radiating part 520 thatincludes plural parallel plate-shaped fins 522 that extend from the base510 perpendicular to the motherboard or in a direction Z in FIG. 18. Thehead sink 600 includes a base 610 placed on an exoergic component (notshown) mounted on a motherboard (not shown), and a radiating part 620that includes plural pinholder-shaped fins 522 that extend from the base610 perpendicular to the motherboard or in a direction Z in FIG. 20.

[0006] A fan-cum-heat sink that includes a fan has been proposed toenhance a cooling effect of the heat sink. The fan-cum-heat sinkprovides forced-air cooling to the heat sink with air currents producedby a fan.

[0007] A higher speed and more functions of various circuit elementshave drastically increased the calorific values from the circuitelements, and required the heat sink to have higher heat radiationperformance. Conceivably, this request would be met by increasingsurface areas of the radiating parts 520 and 620 in the conventionalheat sinks 500 and 600.

[0008] A conceivable way of increasing the surface area of the radiatingpart 520 or 620 is to narrow an interval or pitch between fins 522 or622 and increase the number of fins 522 or 622 per unit area and/or tothicken each fin 522 or 622. Both of these methods eventually narrow apitch, and reduce the air convection that passes between the fins 522 or622, lowering the cooling efficiency at center parts of the bases 510and 610 (this condition is sometimes called “increased pressure loss” inthis application).

[0009] It is also conceivable to extend the height of the fins 522 or622 in the height direction or direction Z to increase the surface areaof the radiating part 520 or 620. However, the fin 522 or 622 has such atemperature gradient in the direction Z that the excessively high fin522 or 622 has lowered heat exchanger effectiveness and coolingefficiency on its top. In order to rectify this shortcoming, it is alsoconceivable to replace a material of the fin 522 or 622 with a materialhaving high heat conductivity for the reduced temperature gradient inthe height direction or the direction Z. For example, it is conceivableto replace aluminum, typically used for the fins 522 and pins 622, whichhas heat conductivity of 203 W/m·K with copper that has heatconductivity of 372 W/m·K. However, copper needs anti-oxidant coating,and complexes the manufacture process. In addition, copper is heavierthan aluminum and an undesirable material to be attached to a top of thecomponent. The length in the direction Z is restricted by the mountingspace limitation in the PC.

[0010] It is also conceivable to attach a fan to a heat sink to enhancethe heat conductivity, but this deteriorates energy saving aspect andeconomical efficiency of the heat sink.

[0011] Thus, some parameters should be considered which include thepressure loss instead of merely increasing the surface area of the finin order to enhance the heat radiation efficiency in a heat sink.

BRIEF SUMMARY OF THE INVENTION

[0012] Accordingly, it is a general object of the present invention toprovide a novel and useful heat radiator mechanism and electronicapparatus having the same in which the above disadvantages areeliminated.

[0013] Another exemplified and more specific object of the presentinvention is to provide a heat radiator mechanism and electronicapparatus having the same, which comparatively inexpensively enhance theentire heat radiation efficiency taking into account some parametersincluding pressure loss.

[0014] A heat sink of one embodiment according to the present inventionincludes a heat receiving part for receiving heat from the outside, afirst radiating part, connected to the heat receiving part, which formsa first air channel, and radiates the heat from the heat receiving partusing air that passes through the first air channel, and a secondradiating part, located apart from the heat receiving part and connectedto the first radiating part, the second radiating part forming a secondair channel which the air that has passed the first air channel enters,the second air channel being narrower than the first air channel, thesecond radiating part radiating the heat from the first radiating part.This heat sink may radiate the heat from the heat receiving part usingthe first and second radiating parts. The first radiating part forms thefirst air channel, and radiates the heat as a result of that the airpasses through the first air channel. The air that has passed throughthe first air channel may enter the second air channel of the secondradiating part narrower than the first air channel, and the secondradiating part may radiate the heat using the air convection. The secondradiating part is spaced from the first radiating part by apredetermined distance that contributes to definition of the first airchannel at the first radiating part. The first radiating part of theheat sink includes, for example, plural fins, and the second radiatingpart is provided between two fins, thereby maintaining the second airchannel. The sufficiently large second air channel may be maintained byproviding the second radiating part with second fin thinner than thefirst fin. Moreover, this heat sink forms a surface area of the secondradiating part larger than that of the first radiating part, maintainsthe sufficiently wide heat radiation area and enhances the heatradiation effect. The heat sink includes a side plate that encloses thesecond radiating part and defines an air channel, so as to assist thesecond radiating part in radiating the heat. The second radiating partincludes a first part near a center, and a second part, located outsidethe first part, which has a larger surface area than the first part. Awide heat radiation area may be obtained by forming the first partlarger than the second part that promotes the air convection. A similaroperation may be obtained by making the second part longer than thefirst part in the height direction. Alternatively, the first part longerthan the second part in the height direction would promote the airconvection at the first part and enhance the heat radiation efficiency.The convection at the second radiating part may be promoted and the heatradiation efficiency may be promoted by forming a notch in the thinplate, and raising the notch to form a raised piece as a bent projectionand disturb the airflow. This notch may connect adjacent second airchannels. The increased number of pillar parts and a shape of the pillarpart would promote the air convection and enhance the heat radiationefficiency.

[0015] An electronic apparatus of another embodiment according to thepresent invention includes a printed board mounted with an exoergiccomponent, and a heat sink, provided on the printed board, which coolsthe exoergic component, wherein the heat sink includes a heat receivingpart for receiving heat from the outside, a first radiating part,connected to the heat receiving part, which forms a first air channel,and radiates the heat from the heat receiving part using air that passesthrough the first air channel, and a second radiating part, locatedapart from the heat receiving part and connected to the first radiatingpart, the second radiating part forming a second air channel which theair that has passed the first air channel enters, the second air channelbeing narrower than the first air channel, the second radiating partradiating the heat from the first radiating part. This electronicapparatus has the above heat sink, and exhibits similar operations tothose of the heat sink.

[0016] Other objects and further features of the present invention willbecome readily apparent from the following description of theembodiments with reference to accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a schematic perspective view near a heat sink as oneembodiment according to the present invention that is applied to amotherboard in a PC.

[0018]FIG. 2 is a schematic top view of the heat sink shown in FIG. 1.

[0019]FIG. 3 is a schematic sectional view of the heat sink shown inFIG. 2 taken along line X-X.

[0020]FIG. 4 is a schematic sectional view of the heat sink shown inFIG. 2 taken along line Y-Y.

[0021]FIG. 5 is a schematic top view of the heat sink having aplate-shaped fin as a variation of a pillar part shown in FIG. 1.

[0022]FIG. 6 is a schematic sectional view of the heat sink shown inFIG. 5 taken along line X-X.

[0023]FIG. 7 is a schematic sectional view of the heat sink shown inFIG. 5 taken along line Y-Y.

[0024]FIG. 8 is a schematic top view of the heat sink having aplate-shaped fin as a variation of a pillar part shown in FIG. 1.

[0025]FIG. 9 is a schematic sectional view of a variation of a thinplate of a radiating part in the heat sink shown in FIG. 1.

[0026]FIG. 10 is an enlarged perspective view of a circle shown in FIG.9.

[0027]FIG. 11 is a schematic perspective top view of a heat sink havinga thin plate as a variation of a thin plate shown in FIG. 1.

[0028]FIG. 12 is a schematic plane view of a variation of a side plateof the heat sink shown in FIG. 1.

[0029]FIG. 13 is one schematic side view of the heat sink shown in FIG.12.

[0030]FIG. 14 is another schematic side view of the heat sink shown inFIG. 12.

[0031]FIG. 15 is a schematic sectional view of the heat sink shown inFIG. 1 provided with a cavity.

[0032]FIG. 16 is a schematic sectional view of the heat sink shown inFIG. 15 provided with a fan.

[0033]FIG. 17 is a view that compares cooling performance of aconventional heat sink with that of the inventive heat sink.

[0034]FIG. 18 is a schematic side view of a structure of theconventional heat sink.

[0035]FIG. 19 is a schematic top view of the heat sink shown in FIG. 18.

[0036]FIG. 20 is a schematic side view of a structure of theconventional heat sink.

[0037]FIG. 21 is a schematic top view of the heat sink shown in FIG. 20.

DETAILED DESCRIPTION OF THE INVENTION

[0038] A description will now be given of a heat sink as a radiatormechanism of one embodiment according to the present invention, withreference to FIGS. 1 to 4. FIG. 1 is a schematic perspective view near aheat sink 100 as one embodiment according to the present invention thatis applied to a motherboard 200 in a PC 300. FIG. 2 is a schematic topview of the heat sink 100. FIG. 3 is a schematic sectional view of theheat sink 100 shown in FIG. 2 taken along line X-X. FIG. 4 is aschematic sectional view of the heat sink 100 shown in FIG. 2 takenalong line Y-Y. The same element in each figure is designated by thesame reference numeral, and a duplicate description thereof will beomitted. The reference numeral with an alphabet generally denotes avariation, and the reference numeral without an alphabet generalizes allthe same reference numerals with different alphabets.

[0039] The heat sink 100 is placed on a CPU 210 (which includes an MPUand any other processor irrespective of its name) as an exoergiccomponent mounted on the motherboard 200 shown in FIG. 1. The heat sink100 includes a heat receiving part 110, a pillar part 120, a radiatingpart 130, and side plate 170.

[0040] The heat receiving part 110 thermally contacts an exoergiccomponent outside the heat sink 100 and receives heat from it. Theinstant embodiment places the heat receiving part 110 directly on theCPU 210, but the present invention allows the heat receiving part 110 toindirectly contact the CPU 210 via a certain member. The heat receivingpart 110 has a rectangular plate shape in the instant embodiment, butmay have an arbitrary shape according to shapes of exoergic componentsto be connected to the heat receiving part 110. The heat receiving part110 has a bottom area surface (e.g., 40 mm×40 mm) that is approximatelythe same as or larger than the top surface area of the CPU 210 so thatit may receive heat from the entire surface of the CPU 210. Thethickness of the heat receiving part 110 is not limited, but the heatreceiving part 110 preferably is made as thin as possible for effectiveheat conduction to the pillar 120, which will be described later. Theheat receiving part 110 is made, for example, of such a material havinghigh thermal conductivity as aluminum.

[0041] The heat receiving part 110 has a heat receiving surface 112 as asurface that surface-contacts the CPU 210, a heat radiator surface 114as a surface opposite to the heat receiving surface 112 and at the sideof the pillar 120, and four side surfaces 116. The inventive heat sink100 absorbs the heat generated from the CPU 210 through the heatgenerating surface 112, and transfers the heat to the pillar part 120 atthe heat radiator surface 114. Of course, the heat receiving part 110may radiate the heat at the heat radiator surface 114 and side surfaces116. The heat receiving part 110 may be formed integral with the pillarpart 120, or formed independent of the pillar part 120 and then jointedtogether.

[0042] The pillar part 120 serves as a first heat radiator part thatradiates the heat from the heat receiving part 110, and conducts part ofthe heat received from the heat receiving part 110 to the heat radiatorpart 130. The pillar part 120 of the instant embodiment is made ofplural approximately T-shaped plate-shaped fins 122 which are arrangedin parallel. However, as described below with reference to FIG. 8, theinventive plate-shaped fins 122 do not have to be necessarily arrangedin parallel. As described below with reference to FIG. 5, the presentinvention does not limit the shape of the pillar part 120 to a plateshape, and may use the pillar part 120 with a pin shape or any othershape.

[0043] The pillar fins 122 stand erect from the heat radiator surface114, and a vent 128 shown in FIG. 1 is connected between two fins 122.The vent 128 is connected to the outside, and maintains, with two fins122, a first air channel for cooling. The first air channel contributesto air cooling to the heat radiator surface 114, fins 122, and heatradiator part 130, which will be described later.

[0044] Referring to FIG. 3, the plate-shaped fin 122 of this embodimenthas an approximately T-shape, and includes a lower part 123 (below adotted line in FIG. 3) formed as wide as the heat receiving part 110,and an upper part 124 (above the dotted line in FIG. 3) connected to theheat radiator part 130 and formed wider than the lower part 123. Thelower part 123 has a height h, for example, of about 7 mm. The height hof zero would eliminate the vents 128, and undesirably enlarge thepressure loss. The height h having a value near zero would reduce thevents 128, and undesirably enlarge the pressure loss. The height hdiffers depending upon use or nonuse of a fan, even when the same heatradiator effect is expected. As will be described later, the heatradiator part 130 is spaced from the heat receiving part 110 by theheight h. As detailed later, as shown in FIG. 2, the instant embodimentforms the upper part 124 and the heat radiator part 130 larger than thetop surface of the heat receiving part 110. Therefore, when the height hbecomes zero, the upper part 124 and heat radiator part 130 undesirablyprevent a memory and other circuit elements from being mounted in aspace 202 shown in FIG. 1 adjacent t the CPU 210 on the motherboard 200.Therefore, the height h of about 5 mm or larger, more preferably 7 to 10mm, is necessary even when the fan is used.

[0045] The upper part 124 of the pillar part 120 is wider (e.g., about60 mm) than the lower part 123, and maintains a wide heat radiator area.A shape of the plate-shaped fin 122 of this embodiment is exemplary forthis advantage, and the present invention may use a trapezoid-shapedplate-shaped fin.

[0046] As shown in FIGS. 1 and 4, the pillar part 120 of the instantembodiment is made of five plate-shaped fins 122. The number ofplate-shaped fins 122 is exemplary, and the present invention is notlimited to this number. An interval d between adjacent plate-shaped fins122 defines the above first air channel to the heat radiator part 130.As the airflow is in proportion to product between the height h and theinterval d, the interval d is determined for the intended airflow. Theinterval d is set to, for example, about 7 to 11 mm, and 9 mm in theinstant embodiment. As shown in FIG. 4, each plate-shaped fin 122 hasthe same size and shape with a common thickness t in the instantembodiment. As the thickness t increases, the surface area of the fin122 generally increases, narrowing the interval d. The excessively smallthickness t would enlarge the temperature gradient to the tip (or top inFIG. 4) of the pillar part 120, and lower the heat conductionperformance and thus the heat conductivity from the pillar part 120 tothe heat radiator part 130. The thickness t was set in view of thispoint. The thickness t is set, for example, about 1 to 2 mm, and about 2mm in the instant embodiment.

[0047] The pillar part 120 is made, for example, of such a materialhaving high thermal conductivity as aluminum. As discussed above, thepillar part 120 may be formed integral with the heat receiving part 110.When the pillar part 120 is formed as a single member, the pillar part120 is provided on the side of the heat receiving surface 114 of theheat receiving part 110 through such means as adhesion and welding.

[0048] As discussed above, the pillar part 120 is not limited to theabove T shape, and may include a plate-shaped fin 122, as shown in FIGS.5 to 7, which divides one plate-shaped fin 122 into plural pieces usingslits 125. Here, FIG. 5 is a schematic top view of the heat sink 100having a plate-shaped fin 122 b as a variation of a pillar part 120shown in FIG. 1. FIG. 6 is a schematic sectional view of the heat sink100 shown in FIG. 5 taken along line X-X. FIG. 7 is a schematicsectional view of the heat sink 100 shown in FIG. 5 taken along lineY-Y.

[0049] The slit 125 between adjacent plate-shaped fins 122 b in thedirection X in FIG. 5 may be connected to the above vents 128 bydividing the plate-shaped fin 122 into plural pieces, enlarging a rangeof the airflow. This shape promotes the air convection and may improvethe heat radiation efficiency of the heat sink 100. The plate-shaped fin122 b may be provided with the slits 125 only at the upper part 124 b soas not to reduce the heat conductivity to the radiating part 130 at theupper part 124 above the pillar part 120, or may be provided with theslits 125 to middle part between the upper and lower parts 124 and 123b. Understandably, similar operations and effects are available byproviding the fin 122 with a notch or any other hole instead of the slit125 and connecting the notch etc. to the above vents 128.

[0050] As discussed above, the arrangement of the plate-shaped fin 122of the pillar part 120 is not limited to a parallel and lateralarrangement. For example, as shown in FIG. 8, plural arc-shaped fins 122c may be arranged concentrically. Here, FIG. 8 is a schematic top viewof the heat sink 100 having a plate-shaped fin 122 c as anothervariation of the pillar part 120 shown in FIG. 1. This arrangement mayalso exhibit similar operations of the plate-shaped fin 122 having theabove structure.

[0051] The radiating part 130 is located at the upper part 124 of thepillar part 120, and serves as a second radiating part that radiates theheat from the pillar part 120. The radiating part 130 has a thin plate132. The instant embodiment provides the radiating part 130 between thefins 122, but the radiating part 130 does not have to be providedbetween fins 122, and may be provided onto the lower part 123 byremoving the upper part 124. As shown in FIGS. 2 and 4, the radiatingpart 130 respectively arranges thin plates 132 orthogonal to the heatreceiving part 110 between the plate-shaped fins 122. The radiating part130 uses the thin plate 132 to radiate the heat absorbed from the heatreceiving part 110 and transmitted to the pillar part 120.

[0052] The thin plate 132 has a plate thickness smaller than thethickness t (which is 0.2 mm in this embodiment) of the plate-shaped fin122 of the pillar 120, and its section is bent like a corrugated shape.Of course, the thin plate 132 may have various sectional shapes, such asany other waveform shape, a U-shape, a V-shape, and a W-shape. As thethin plate 132 intends to enlarge the surface area of the pillar part120, the present invention covers a non-bent shape, for example adiagonally provision between two adjacent pillar parts 120's upper parts124.

[0053] As shown in FIG. 2, the thin plate 132 forms bent portions sothat they may contact the plate-shaped fin 122, and defines a second airchannel in an airflow direction from the lower part 123 of theplate-shaped fin 122 to the upper part 124 (or from the upper part 124to the lower part 123). The thin plate 132 has the approximately thesame size as the upper part 124 of the plate-shaped fin 122. Such acorrugated bending interval is applied to the thin plate 132 so as notto prevent the airflow at the radiating part 130. As shown in FIG. 2,the passages 134 as the second air channel defined by the thin plate 132are connected to the above vents 128.

[0054] The thin plate 132 radiates the heat conducted by the thin plate132 via a contact portions with the plate-shaped fin 122. The corrugatedthin plate 132 may maintain a large surface area. In other words, thethin plate 132 expands the heat radiation area between the plate-shapedfins 122. The thin plates 132 maintain larger heat radiation area and donot reduce the heat radiation efficiency of the heat sink 100 even whenthe plate-shaped fins 122 of the pillar part 120 have such a wide finpitch as allows the uniform air convection. The thin plate 132 isthinner than the plate-shaped fin 122, and does not prevent the airnatural convection.

[0055] The thin plate 132 is made, for example, of such a materialhaving high thermal conductivity as aluminum. The thin plate 132 is sothin that its weight would not be problematic, and thus may use anothermaterial having high thermal conductivity, such as copper, to enhancethe heat radiation efficiency. When the thin plate 132 is made ofaluminum, the thickness of the thin plate 132 is between 0.1 and 0.3 mm.When the thin plate 132 is made of copper, the thickness of the thinplate 132 is between 0.05 and 0.15 mm, about half that for aluminum.

[0056] Referring to FIGS. 9 and 10, the thin plate 132 may be replacedwith a thin plate 132 a that has a plurality of raised pieces 133. FIG.9 is a schematic sectional view of the thin plate 132 a as a variationof the thin plate 132. FIG. 10 is an enlarged perspective view of acircle shown in FIG. 9. The raised piece 133 is provided on a plane area136 of the thin plate 132 a, which is not subject to bending. The raisedpiece 133 is formed by forming a notch 135 in the plane area 136 of thethin plate 132 a, raising a top of the notch 135, and deforming theplane area 136. Each plane area 136 may form a plurality of raisedpieces 133. The raised pieces 133 are preferably formed on each planearea 136 of the thin plate 132 a. The thin plate 132 a uses the raisedpieces 133 to disturb airflow that convects on the thin plate 132, andthus promotes turbulence and enhances the heat conductivity. Therefore,the raised pieces 133 promote the air convection on the thin plate 132a, and assist in enhancing the heat radiation efficiency. The thin plate132 may exhibit this operation by forming a projection on its surface,and thus is not limited to the above embodiment.

[0057] The raised pieces 133 on the thin plate 132 a have an effect tointroduce the air that convects on the thin plate 132 a into the notch135. In other words, the airflow may be expanded simply by providing aperforation in the thin plate 132. The air introduced through the vents128 ascends vertical to the heat receiving part 110, and the raisedpieces 133 in the instant embodiment assist the air in passing throughthe notch 135. Therefore, the raised pieces 133 also promote the airconvection on the thin plate 132 a, and enhance the heat radiationefficiency.

[0058] The side plate 170 is a frame that encloses the plate-shaped fins122 and the thin plate 132 located at the outermost plate-shaped fin122, as best shown in FIGS. 2 to 4. The side plate 170 is formed withapproximately the same thickness as the plate-shaped fin 122. The sideplate 170 has a shape by adhering four plates, or a hollow square pole.A provision of the side plate 170 would be able to prevent leakage ofwind from the outermost thin plates 132. In other words, the side plate170 maintains the air channel, and controls the airflow at the radiatingpart 130 (in particular, near the thin plate 132 located at theoutermost part). This side plate 170 is especially effective when theheat sink 100 is provided with a fan (not shown). The side plate 170 mayradiate the heat conducted from the pillar part 120 and the thin plate132 due to the heat conduction associated with the air convection.

[0059] The air convection is promoted at the side of the thin plate 132located at both ends compared with the center part of the radiating part130. Therefore, as shown in FIG. 11, the outermost thin plates 132 ofthe plate-shaped fin 122 may be replaced with a thin plate 132 b shownin FIG. 11. Here, FIG. 11 is a schematic perspective top view of a heatsink 100 having the thin plate 132 b as another variation of the thinplate 132 shown in FIG. 1. The thin plate 132 b is bent so that aninterval smaller than the thin plate 132 between the plate-shaped fins122. The thin plate 132 b has a surface area larger than that of thethin plate 132, and thus expands the heat radiation area effectively. Asdiscussed above, since the air convection is promoted at the side of thethin plates 132 b located at both ends, a narrow interval of the thinplate 132 b does not weaken the air convection.

[0060] The heat radiator part 130 may replace the side plate 170 with aside plate 17 a shown in FIGS. 12 to 14. Here, FIG. 12 is a schematicplane view of the heat sink 100 having the side plate 170 a as avariation of the side plate 170 shown in FIG. 1. FIG. 13 is oneschematic side view of the heat sink 100 shown in FIG. 12. FIG. 14 isanother schematic side view of the heat sink 100 shown in FIG. 12. Theside plate 170 a is formed higher than the side plate 170, and as highas the plate-shaped fin 122. Therefore, the side plate 170 encloses thepillar part 120 entirely. However, the side plate 170 a at the sideorthogonal to the plate-shaped fin 122 is formed as high as the sideplate 170 at a portion 172 corresponding to the pillar part 120 so asnot to prevent the air inflow to or near the center of the heat sink100. In this state, the outermost thin plate 132 c of the pillar part120 is longer than the thin plate 132 between the plate-shaped fins 122.More specifically, the thin plate 132 c is as high as the side plate 170a. The thin plate 132 c may be formed higher than the thin plate 132 byelongating the side plate 170 a, and the surface area of the radiatingpart 130 may be expanded further. As discussed, since the air convectionis promoted at the side of the thin plate 132 c located at both ends,the long side plate 170 and thin plate 132 do not weaken the airconvection near the thin plate 132 c.

[0061] On the other hand, referring to FIG. 15, the heat sink 100 mayhave a cavity 140 different from the shape shown in FIGS. 11 to 14.Here, FIG. 15 is a schematic sectional view of the heat sink 100 shownin FIG. 1 provided with the cavity 140. The cavity 140 is a shape convexcavity projecting down at the side opposite to the heat receiving part110 near the center part of the radiating part 130 and the pillar part120. A provision of this cavity 140 would shorten the radiating part 130near the center part. Therefore, the air convection is promoted near thecenter part of the radiating part 130 and provides the enhanced heatradiation efficiency when compared with a structure without the cavity140. Referring to FIG. 16, this shape is effective when the fan 150 isprovided 150. FIG. 16 is a schematic sectional view of the heat sink 100shown in FIG. 15 provided with a fan 150. When the top of the heat sink100 is provided with the fan 150, the fan center part 152 is such acenter of rotation of the fan 150, and causes less air convection.However, a provision of the cavity 140 would be able to introduce theair from a fan end 154, and improve the heat radiation efficiency of theradiating part 130 (especially at the center part). The fan 150 is alsocalled a cooler, and protects the CPU 210 from the heat by compulsorilyradiating the heat. A lid is preferably provided to reduce noisesassociated with a rotation of the fan 150.

[0062] The fin 122 and the radiating part 130 are compulsorily cooled byrotating the fan 150 and generating the airflow. The fan 150 includes amotor portion (not shown), a propeller portion 151 fastened to the motorportion. The motor portion typically includes an axis of rotation, abearing provided around the axis of rotation, a bearing house, and amagnet making up a motor, but since any structure known in the art maybe applied to the motor portion 132, a detailed description will beomitted. In order to prevent heat transfer to the bearing house, athermal insulation portion is preferably formed on an inner wall surfaceof the bearing house. The thermal insulating portion is, for example,formed of such a material having low thermal conductivity asfluoroplastic and silicon resin thin films.

[0063] The propeller portion 151 includes a desired number of rotorblades each forming a desired angle. The rotor blades may be so orientedto form equal or unequal angles, and have a desired dimension. The motorportion and propeller portion 151 in the fan 150 may be separable ornon-separable. An illustration of wiring connected with the fan 150 isomitted. When a perforation or intake is formed in the space 202 shownin FIG. 1, the fan 150 may take in air from the both sides of themotherboard 200 through the perforation.

[0064] As discussed above, the heat sink 100 includes three parts, i.e.,the heat receiving part 110, pillar part 120, and radiating part 130,enlarges the heat radiation area without disturbing the air convection,and improves the heat radiation efficiency. In this embodiment, theplate-shaped fin 122 of the pillar part 120 integrates the upper part124 with the lower part 123, although the upper part 124 may bedetachable from the lower part 123 in the plate-shaped fin 122 and onlythe lower part 123 constructs the pillar part 120. In other words, theradiating part 130 includes the upper part 124 of the plate-shaped fin122 and the thin plate 132. The radiating part 130 in this structure mayproperly vary its size and shape in accordance with the intended heatradiation performance. Of course, this state maintains the heattransferable from the pillar part 120 to the radiating part 130. In use,the pillar part 120 is adhered to the radiating part 130.

[0065] Referring to FIG. 17, it is apparent that the inventive heat sink100 has superior heat radiation performance or cooling performance tothat of the conventional heat sink 600. Here, FIG. 17 is a view thatcompares cooling performance of the conventional heat sink 600 with thatof the inventive heat sink 100. In FIG. 17, the conventional heat sinkis shown like a rhomb, the heat sink 100 shown in FIG. 1 is shown as atriangle, and the heat sink 100 shown in FIG. 12 is shown as a square.The abscissa axis denotes a fin pitch (mm), while the ordinate axisdenotes the cooling performance (W). The inventive fin pitch is aninterval between adjacent pillar parts. As understood from FIG. 17, theinventive heat sink 100 has superior cooling performance to that of theconventional heat sink 600. A large fin pitch value slightly drops thecooling performance, whereas the conventional heat sink 600 remarkablylowers cooling performance with fin pitch. In other words, the enlargedfin pitch in the conventional heat sink 600 would lead to a smaller heatradiation area and clearly lower the cooling performance. It isunderstood that the present invention maintains the heat radiation areaat the thin plates 132 and side plate 170, and the enlarged intervalbetween pillar parts 120 do not lower the cooling performance so much.

[0066] Turning back to FIG. 1, a description will be given of the PC 300to which the inventive heat sink 100 is applicable. The PC 300 has ahousing (not shown), and accommodates the motherboard 200 and a harddisc drive (“HDD”) and floppy disc drive (“FDD”) (not shown). Theinstant embodiment uses the desktop PC, but the PC 300 may be a towertype. The PC 300 includes a display as an output part (not shown), and akeyboard and mouse as an input part (not shown). The display, keyboard,and mouse may use any technology known in the art, and a detaileddescription will be omitted in this specification.

[0067] The motherboard 200 typically includes a socket (not shown) forattaching the CPU 210 and a memory, and an expansion slot to which anexpansion card is attached. Each part may be electrically connected byattaching the CPU 210 as a control part and a memory (not shown) as amain storage to the motherboard 200. The socket for attaching the CPU210 covers both a socket and a slot, and a shape of the socket is notlimited. Similarly, a shape of the socket for the memory is not limited.

[0068] The motherboard 200 mounted with the CPU 210 has the heat sink100 on the CPU 210 at the side opposite to the motherboard 200. The heatsink 100 surface-contacts the CPU 210 through the heat receiving surface12 of the heat receiving part 110. The heat sink 100 and the CPU 210 arefixed together by a clip (not shown). This clip holds the heat receivingpart 110 and the CPU 210 using as the vent 128 of the pillar part 120for a perforation of the clip. The heat sink 100 may use any structurethat has been discussed above, and a detailed description will beomitted. The fan 150 may be provided, as shown in FIG. 16, to the heatsink 100 at the side opposite to the CPU 210 so as to enhance the heatradiation efficiency. Whether the fan 150 is provided is optional anddetermined by the intended cooling performance. The fan 150 may use atype that blows up the air from the side of the heat receiving part 110to the side of the radiating part 130, or a type that blows up the airfrom the radiating part 130 to the heat receiving part 110.

[0069] The PC has a HDD and FDD as an auxiliary storage. The HDD is aunit that moves an arm on a disc to which a magnetic material isattached for reading and writing. The HDD and FDD may use any technologyknown in the art, and a description thereof will be omitted.

[0070] In operation, a user of the desktop PC 300 executes a programstored in the HDD manipulating the keyboard and/or mouse. The CPU 210downloads necessary data from the HDD and the ROM (not shown) to thememory. The heat generated from the CPU 210 transfers to the radiatingpart 130 of the heat sink 110 through the heat receiving part 110 andthe pillar part 120. As a result, the heat is radiated from surfaces ofthe thin plate 132 and side plate 170 of the radiating part 130 (aircooling). Of course, the heat is radiated from the radiating surface 114of the heat receiving part 110 and the pillar part 120 due to the heatconduction associated with the air convection. Blast from the fan 150shown in FIG. 16 would compulsorily cool the radiating part 130.

[0071] Further, the present invention is not limited to these preferredembodiments, and a various variations and modifications may be madewithout departing from the spirit and scope of the present invention. Ifrequired, the side plate 170 and other members may include a hollowbottom portion having the bottom surface 124, in which cooling water orother refrigerants (e.g., fleon, alcohol, ammonia, galden, and flon) arecontained to form a heat pipe plate. In addition, the side plate 170 andother members, if necessary, may be connected with an external heatpipe, or the like. This heat pipe may include a pipe with a differenceof elevation made of aluminum, stainless, copper, or the like. The pipehas a wick material made of glass fiber, reticular thin copper wire, orthe like affixed inside, and under reduced pressure, stores coolingwater or other refrigerants. The cooling water cools exoergic componentsby repeating the following cycle: having obtained heat from the exoergiccomponents in a lower position, the cooling water is vaporized and movesup to a higher position, and then is spontaneously or forcefully cooledin the higher position, liquefied, and returns to the lower position.The heat pipe when connected to a specific exoergic source would coolthe source efficiently or intensively.

[0072] The inventive heat sink spaces the heat receiving part from theradiating part by a certain height, and allows air inflow to theradiating part in this height. A structure that provide a weightapproximately below the head with respect to the balancer section, and astructure that bends and spaces the balancer section from the disc maymechanically stabilize the weight balance of the balancer section, andeffectively reduce the torsion. Moreover, use of the preamp IC for theweight would be able to improve the electric characteristics. Even whenthe thin plate provided on the radiating part reduces the number ofpillar parts, a sufficient heat radiating area may be maintained and theheat radiating efficiency may be enhanced in comparison with theconventional one. When the thin plate is bent to form a corrugated shapeand/or to form a narrow bending interval, the surface area andconsequently the heat radiation area may increase. The raised pieces onthe thin plate may disturb the airflow, and promote the convection atthe radiating part. The increased number of the pillar parts and a shapeof the pillar part may promote the air convection and improve the heatradiation efficiency.

What is claimed is:
 1. A heat sink comprising: a heat receiving part forreceiving heat from the outside; a first radiating part, connected tosaid heat receiving part, which forms a first air channel, and radiatesthe heat from said heat receiving part using air that passes through thefirst air channel; and a second radiating part, located apart from saidheat receiving part and connected to said first radiating part, saidsecond radiating part forming a second air channel which the air thathas passed the first air channel enters, the second air channel beingnarrower than the first air channel, said second radiating partradiating the heat from said first radiating part.
 2. A heat sinkaccording to claim 1, wherein said first radiating part includes pluralfins, and said second radiating part is provided between two fins.
 3. Aheat sink according to claim 1, wherein said first radiating part has afirst fin, and said second radiating part has a second fin thinner thanthe first fin.
 4. A heat sink according to claim 1, wherein said secondradiating part has a larger surface area than said first radiating part.5. A heat sink according to claim 1, further comprising a side platethat encloses said second radiating part and defines an air channel. 6.A heat sink according to claim 1, wherein said second radiating partincludes: a first part located at a position corresponding to a centerof the heat receiving part; and a second part, located outside the firstpart, which has a larger surface area than the first part.
 7. A heatsink according to claim 1, wherein said second radiating part includes:a first part located at a position corresponding to a center of the heatreceiving part; and a second part, located outside the first part, whichhas a longer than the first part in a height direction.
 8. A heat sinkaccording to claim 7, wherein the first part has such a height in theheight direction that the second air channel at the first part issmaller than the second air channel at the second part.
 9. A heat sinkaccording to claim 1, wherein said second radiating part includes aprojection that disturbs airflow in the second air channel.
 10. A heatsink according to claim 1, wherein said second radiating part includes anotch that assists inflow of the air.
 11. A heat sink according to claim1, wherein said first radiating part becomes wider with distance fromsaid heat receiving part.
 12. A heat sink according to claim 1, whereinsaid first radiating part has a fin with a notch connected to the firstair channel.
 13. A heat sink according to claim 1, wherein said firstradiating part has plural fins, which have a slit connected to the firstair channel between adjacent fins.
 14. An electronic apparatuscomprising: a printed board mounted with an exoergic component; and aheat sink, provided on said printed board, which cools the exoergiccomponent, wherein said heat sink includes: a heat receiving part forreceiving heat from the outside; a first radiating part, connected tosaid heat receiving part, which forms a first air channel, and radiatesthe heat from said heat receiving part using air that passes through thefirst air channel; and a second radiating part, located apart from saidheat receiving part and connected to said first radiating part, saidsecond radiating part forming a second air channel which the air thathas passed the first air channel enters, the second air channel beingnarrower than the first air channel, said second radiating partradiating the heat from said first radiating part.